I would like to know if there is a safe way to switch between 2 guitar cabinets?I'm using a 60W tube (fender style amp) and I would like to build an A/B (or even A+B) (foot)switcher box to chose between 2 cabinets (Both 8 ohm).I know the Radial box but it's way too expensive for me.I've heard of a switcher that uses relays, but I haven't got any clear information.I've also read about a passive box with resistors and a switch but it's not exactly what I was thinking since it's working only with the amp bypassed.Any ideas, info or layouts (or schematic) on how to build such a box would be much appreciated.

Any relay that can handle the current ( 60W in 8 Ohm gives 2.7A , so go for 5A ) will do the job. Be sure not to hit the strings when switching, the amp must have no output when switching, because for a fraction of time, your tube-amp will see no load.

I've used a system like this for years without it ever causing any issues on any valve amp I've been tinkering with. The split second no load thing has never been an issue - and I've had 400W bass amps running through it.

BlueMeany wrote:Just go for it using some decent (well over spec!) relays.

I've used a system like this for years without it ever causing any issues on any valve amp I've been tinkering with. The split second no load thing has never been an issue - and I've had 400W bass amps running through it.

Technically that is quite dangerous. Some years ago someone did a "spark gap" test with a similar setup.

You could easily use a SPDT relay to alternately short out a cabinet and have a "split second Series load" situation. Using a "make-before-break" switch, where the output is shorted, would also be safer.

1)Could you please share a layout or schematic and specs for the relays?2)Why relays and not heavy duty switches (like car dimmer switches) ?3) Is it possible to make it A, B, Y with two relays?4)What about the MBB switch? Where in the circuit? What specs?

BlueMeany wrote:Just go for it using some decent (well over spec!) relays.

I've used a system like this for years without it ever causing any issues on any valve amp I've been tinkering with. The split second no load thing has never been an issue - and I've had 400W bass amps running through it.

Technically that is quite dangerous. Some years ago someone did a "spark gap" test with a similar setup.

You could easily use a SPDT relay to alternately short out a cabinet and have a "split second Series load" situation. Using a "make-before-break" switch, where the output is shorted, would also be safer.

I've used it on probably hundreds of amps, switching them thousands of times between cabs. Never had any problems. It's tried and tested 100%.